SU1765779A1 - Digital frequency meter - Google Patents

Description

(21T4 5T646 / 2G

(22) 07.19.90

(46) 30.0992. Bul №36

(72) B.H Chinkov, Yu A. Nemshilov, and V.A.Berna DSYS

(56) USSR author's certificate

No. 1307365 Cl. G 01 R 23/00, 1987.

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 Isoorten is not related to digital electrical measuring technology and can be used to measure and monitor PGSSHTGettingGga-rmoi eskykh syaYaizb. :

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 The drawing shows a structural arrangement of the digital frequency of it a, “L. fviv "., i

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The input of the frequency meter is connected to the first one, the power source in the DMA and the L61-6-AIF converter (ADC) 1 and to the input of the zero-organ 2, the output of which is connected to the input of smart 1 & H 3 frequency and to the first input of block 4 control Multiplier output 3 hrs GBG-YODSHTGe about yoYyOrItel 5

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the time interval and the first input are ESCHYL AND 6, the second input of which is connected to V o of the control unit 4, and the output I 6 is connected to the second input, i vdrRZHus KTs 1 and the counting input 7 vGorbok the first output, , A / D converters 1 and 2, inf 5 rm of the rating or code, output of the A / D converter 1 is connected to the first one and

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(54) DIGITAL FREQUENCY METER (57) Application: the invention relates to measurement technology and can be used to measure and control the frequency of low-frequency harmonic signals. The digital frequency meter contains an analog-to-digital converter 1 zero-body 2 smart frequency 3, element 6, the counter 7 samples, meter 5 time inter- saia, unit 4 controls, microprocessor calculator 8, unit 9 of indication 1 or

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  G - ib4- - f h S to the second inputs of microprocessor-based calculator 8, and the first, informational or code, output and second output loan output or zero reset (overflow), counter 7 samples - respectively to the third and fourth inputs of the microprocessor The calculator 8, which by its fifth input is connected to the output of the time interval meter 5, the first output to the input of the display unit 9 and the second output to the second input of the control unit 4, the third input of which is connected to the second output of the sample counter.

Control unit 4 contains element 1/1 10, triggers 11, 12, delay element 13, pulse shaper 14, element OR 15, switch 16 Operating mode and button 17 Start. The first input of control unit 4 is connected to the first input of element 10, the second the input of which is connected to the direct output of the trigger 11, and the output of the element Tienta AND 10 with the S input of the trigger 12 The direct output of the trigger 12 is connected to the output of the control unit 4 and to the R input of the trigger 11, the S output of which is connected through in series United element 13 delayed

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ki and pulse shaper 14 to the output of the OR element 15. The pulse shaper 14 output is connected to the reset bus (the fault circuits are not shown in the drawing, in order not to overload the circuit). The three-input element OR 15 is connected to the Start button 17 by its first input, the second input — to the instrument input, the External Start, and the third input — to the first fixed contact of the switch 16 Operating mode, the second fixed contact of which is open, and the movable contact is the second input of control unit 4 .

Digital frequency meter works as follows.

The input signal U (t) is fed to the first signal input of the A / D converter 1 and to the input of the zero-organ 2, the A / D converter 1 is in the standby mode, and the output of the zero-organ 2 produces pulses at times of voltage transition U (t) through the same zero values, for example, from negative to positive. These pulses go to frequency multiplier 3 and through the first input of control unit 4 to the first input of element 10, which is closed at the second input by a low level signal from the direct output of trigger 11. At the output of frequency multiplier 3, a sequence of pulses is formed, the frequency of which follows times the input frequency. In operating mode, these pulses are fed to the second input, the start input, the A / D converter 1 and thereby provide n reference points of instantaneous values of the voltage U (t) uniformly distributed over its period T, i.e. interval (or period) sampling D t T / n. To extend the frequency range, sampling can be used not for one signal period, but with the distribution of sample times over periods, through one or several, using digital signal samplers. Pulses from the output of the multiplier 3 frequencies are fed to the first input of the element 6, which in its initial state is closed at the second input by a low level signal from the direct output of the trigger 12, and to the meter 5 the time interval in which the sampling interval At is measured and the conversion it into a proportional code, which is recorded in its RAM by the 5th input of microprocessor computer 8.

The device has three modes of operation: single, automatic and external start.

Let us consider the operation of the device in the mode of single or manual triggering and signal sampling for one period, which does not change the essence of the invention. In this mode, the switch 16 Mode is set to P, the device is started by the button 17 Start. With her

pressing the output of the pulse shaper 14 generates a pulse, which via the reset bus goes to the installation of the meter 5 of the time interval, the microprocessor computer 8 and the counter 7

0 samples and triggers 11, 12 to the initial state, and then through the delay element 13 to the S input of the trigger 11, switching it to one state. The high level signal from the direct output of the trigger 11 opens element 10 at the second input, and the first impulse from the output of the null organ 2, which arrives after this, passes through element 10 at the counting S input of the trigger 12, setting it to single condition.

0 A high level signal from the direct output of trigger 12 opens element 6 at the second input, and trigger 11 at the R input returns to the initial, zero, state, closing element 10 at the second input.

The output pulses of the zero-organ 2 pass through the open element I 6 to the second input, the start input, the A / D converter 1 and to the counting input of the counter of 7 samples. With the arrival of each start pulse from the output of the element 6 of the A / D converter 1, the binary codes of instantaneous values U (tq) UqjB MOMeHTbi are formed.

5 tq At-q, q 1, n, given by trigger pulses. These codes pulse The conversion coming from the first output of ADC 1 to the first input, recording entry, microprocessor calculator 8, is recorded from the second input, data input, into the RAM of microprocessor calculator 8. The addresses of the recorded Uq codes are given by the output code from the first, information or the code output of the counter of 7 samples fed to the third, address, input of the microprocessor computer 8. The counter of 7 samples also serves to set n samples or samples of instantaneous values of Uq. For this, it is either subtracted and in the initial state the number n for subtraction is written into it, or summing, then in the initial state the number 21 is written in it, n, where I is the counter size. After receipt of

5 pulses from the output of the AND 6 element to the start of the ADC 1, counted by the sample counter 7 samples, and thus after receiving n codes (or samples) of the instantaneous values of the signal Uq at the information output of the ADC 1, the sample counter 7 is zeroed and

An output pulse is formed that goes through the fourth input, the control input, to the microprocessor calculator 8, to the third input of the control unit 4, and to the R input of the trigger 12. Install it in the idle circuit, zero-speed. In addition, the output pulse of the sample counter 7 is restored to its original state (in the diagram, this internal connection of the counting 7 samples is not shown). The low signal of the second input element 6 is closed at the second input and element 6 is passed through it and the pulses to start the ADC 1 stop. The signal from the second output of the counter of 7 samples coming into the microprocessor calculator 8 is removed, the follower follower follower follower follower follower follower follower follower follower follower is used. Uq processing code for obtaining measurement results.

This completes the first stage, the actual measuring stage, and begins at the beginning. computational device operation stage

At this stage, the first, second, third, fourth and fifth inputs of the microprocessor computer 8 are turned off and it is transferred to the automatic mode of operation.

The algorithm of the microprocessor computer is reduced to the following procedures.

First procedure: calculating the amplitude code Um.

The second procedure: calculation of the circular frequency value, which, taking into account the equality tq q-At takes the form:

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L-At „qDm

where L is the number of measurements.

When calculating the cyclic frequency value

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: The results of frequency measurements (w or), as well as, if necessary, other characteristics of the Hermonich signal (amplitude, root-mean-square and average rectified values, period T 1 / f), are outputted by the first micro output U3 & $ & ft, s "4lte" - & a§

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cessor computer 8 in block 9 indications, - --- -

This completes the single or manual measurement process.

When the device operates in the external start mode, switch 1b is also set to state II, but the start-up pulses are not generated by the Start button, but are received at the External Start input, which is necessary when using the device as part of

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When the device is in automatic mode, the switch 16 is set

in position I and the element OR 15, with its third input, is connected to the second output of the microprocessor calculator 8. In this case, the ShpuSgp rybra is performed automatically by pulses arriving

from the second output of the microprocessor computer 8.

Claims (1)

DETAILED DESCRIPTION A digital frequency meter comprising an analog-to-digital converter, a zero-organ, a sample counter, a display unit, and an element, the first input of the analog-digital converter and the input of a zero-organ connected to the input of the device, and the output element I is connected to the second input of the analog-digital converter and the input of the sample counter, characterized in that, in order to increase the accuracy and speed of measurements, a microprocessor computer, a frequency multiplier, a time interval meter and a control unit are inserted into it, while the zero-output is connected to the first input of the control unit and through a frequency multiplier with the input of the time interval meter and the first input of the element I, the second input of which is connected to the output of the control unit, the first, second, third, fourth and fifth inputs of the microprocessor computer are connected respectively to the first and second outputs of the analog-digital converter, to the first and second outputs sample counter and with the output of the time interval meter, and the first and second the outputs of the microprocessor computer are connected respectively to the display unit and the second input of the control unit, the third input of which is connected to the second output of the sample counter, - i.- SRO ETL | YIZK 9s1 fTftaf tg  - jVjttrjf "f3P" l i.